We present a method to construct infrared-finite amplitudes for gauge
theories with massless fermions. Rather than computing S-matrix elements
between usual states of the Fock space we construct order-by-order in
perturbation theory dressed states that incorporate all long-range
interactions. The S-matrix elements between these states are shown to be free
from soft and collinear singularities. As an explicit example we consider the
process e+eββ2 jets at next-to-leading order in the strong coupling. We
verify by explicit calculation that the amplitudes are infrared finite and
recover the well-known result for the total cross section e+eββ hadrons.Comment: 46 page